nsIWebProgress

The nsIWebProgress interface is used to add or remove nsIWebProgressListener instances to observe the loading of asynchronous requests (usually in the context of a DOM window).

nsIWebProgress instances may be arranged in a parent-child configuration, corresponding to the parent-child configuration of their respective DOM windows. However, in some cases a nsIWebProgress instance may not have an associated DOM window. The parent-child relationship of nsIWebProgress instances is not made explicit by this interface, but the relationship may exist in some implementations.

A nsIWebProgressListener instance receives notifications for the nsIWebProgress instance to which it added itself, and it may also receive notifications from any nsIWebProgress instances that are children of that nsIWebProgress instance.